1. Field of the Invention
The present invention generally relates to hydraulic hose fittings. More particularly, it relates to flared cone fittings and more specifically, the present invention relates to improved female portions of flared cone terminations, for tube and hose fittings.
2. Description of the Prior Art
Flared cone fittings are known in the art. Typically, the female portion forms part of a separate fitting or connector that connects a hydraulic hose to a machine, equipment, or fixture or is fixed upon or is a part of a tube that connects the tube to a machine, equipment, or fixture.
As depicted in prior art FIGS. 1 and 2, a female portion of flared cone fitting 100 or 200 includes tube 101, nut 102 or 202, bore 103, and hose stem 104. Hose stem 104 may include ferrule collar 106, hose stop 107, and barbs 109. Tube 101 may be bent as depicted or straight. The end of tube 101 is flared to the point of presenting an inverted conical annulus or cone face 115 at the tube's open end. The inverted conical annulus has an inside diameter substantially equal to the inside diameter of the tube from which the annulus is created.
In one form of the female portion, depicted in prior art FIG. 1 as 110, inverted conical annulus 115 is unsupported by any additional reinforcement. Rather, it merely has an interior shape that corresponds to the exterior shape of the male portion of the coupling, and an exterior shape that corresponds to the interior shape of nut 102. The nut squeezes the conical annulus between itself and the male portion (see FIG. 1). For connecting the female portion to the male portion, a nut having internal threads 120 covering a portion of its interior and having reduced diameter unthreaded portion 121, corresponding to the exterior surface of the inverted conical annulus covering the remaining portion of the nut fits over the tube and about the inverted conical annulus. The male portion has a coned face and external threads proximate the face. Upon connection, the nut is threaded over the external threads of the male portion. The threading action reduces the distance between the coned face and the nut, whereby the inverted conical annulus and the coned face are brought into sealing contact.
When the nut is applied, the inverted conical annulus is secured against the exterior of the male portion, but without give or flexibility. Problematically, tightening of the nut results in a tendency of the nut to seize upon the exterior surface of the inverted conical annulus. In this condition, the torque exerted upon the nut by a wrench is absorbed, interfering with continued tightening of the connection. Application of additional torque in an attempt to overcome the seized condition may merely damage the various components without improving the seal. These problems are not conducive to establishing a leak-tight seal.
In another form of the female portion, depicted in prior art FIG. 2 as 210, inverted conical annulus 115 is supported by collar or sleeve 222, which is fitted upon the tube, in a manner well known in the art, against the exterior surface of the inverted conical annulus. The collar includes abutment 225, orthogonal to the tube. The nut is shaped with corresponding shoulder 221, as well as threads 220. This form is more resistant to seizing, because the forces associated with bringing the inverted conical annulus and the coned face together are mostly devoid of other than axial components. Problematically, this form involves greater cost and complexity. Further, this form also produces a connection without give or flexibility.
Discussion of each of these two forms can be found in Society of Automotive Engineers standards SAE J514 REV. JUN1998 and J533 REV. AUG1996, both of which are incorporated herein by reference.
Both of these joints have significant disadvantages in both production and operation. First, these styles of fittings have a tendency to loosen, leak, and fail under certain conditions. When the female portion is twisted in relation to the male portion of the fitting, such as under the influences of impacts upon the fitting or vibration, the friction between the female portion and the nut can cause the nut to turn and to loosen. This situation is predominantly related to fittings where the tube is bent as depicted in prior art FIGS. 1 and 2, but also applies when the tube is straight. It is believed that the lack of give or flexibility of the connection exacerbates this tendency to loosen. Second, this tendency to loosen can lead an installer of the fitting being encouraged to use additional torque on the fitting to overcome this deficiency, which can lead to failure of the various components, particularly the nut. As stated, the second of the two forms (200) suffers the additional disadvantage of requiring a separate sleeve (222) to be produced and fitted to the tube, adding to the cost and complexity of producing female portion 210 of the flared cone fitting.
Accordingly, there is a continuing need for a flared cone fitting, including a female portion, of simplified construction that has an improved resistance to leakage brought on by loosening caused by twisting of the tube or brought on by too much torque applied to the nut.